Browsing by Subject "Groundwater"
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Item A computer algorithm for improving the day-to-day well field operation for energy conservation(Texas Tech University, 1990-05) Lee, TehfangNot availableItem Aerobic biodegradation of HMX (Octahydro-1,3,5,7-Tetranitro-1,3,5,7-Tetrazocine) with a supplemental study of RDX (Hexahydro-1,3,5-Trinitro-1,3,5-Triazine)(Texas Tech University, 1998-05) Harkins, Victoria A. R.The Pantex facility near Amarillo, Texas, has soil and groundwater contaminated with differing combinations of high explosives (HEs), solvents, and metals. This study is concerned with the treatment of one HE, HMX in produced groundwater. Several physical and chemical treatment schemes for the treatment of HMX have been successful at other sites. These treatments include granular activated carbon adsorption, ultraviolet light radiation in combination with ozone, and alkaline hydrolysis. Successful biological treatment of HMX has been limited to anaerobic environments. Aerobic biodegradation is more desirable because of low capital and operation costs compared to those normally associated with anaerobic treatment. The objective of this work was to identify combinations of microbial consortia and amendments capable of aerobically biodegrading HMX. Once a treatment scheme was identified to breakdown HMX, a supplemental study was undertaken to determine the effects the same conditions would have on RDX, another HE contaminant of concem at Pantex.Item Analysis of the potential impacts of shale gas development(2013-05) Yi, Hyukjoong; Fisher, W. L. (William Lawrence), 1932-The objective of this thesis is to analyze the considerations regarding the environmental impacts of shale gas development by a rational, objective, fact-based assessment. Flowback and produced water from shale gas development can be treated with the related technologies on-site or off-site for recycling, reuse, discharge, and disposal. However, more efficient technologies should be researched even though current levels are high. Besides, the amount of water used in shale gas development is generally lower than that of other energy sources and most shale gas plays are located in areas with moderate to high levels of annual precipitation. However, growing populations, other industrial water demands, and seasonal variation in precipitation should be considered during shale gas development. Groundwater contamination is directly connected to the integrity of the well casing, not hydraulic fracturing, because there are significant spacious gap and several impermeable layers between target formations and ground water zones. Hydraulic fracturing rarely creates unwanted induced seismicity because the seismic energy created from hydraulic fracturing is too low to be detected in the surface, compared to the waste injection well.Item Assessment of the potential for natural attenuation of chlorinated solvents in contaminated groundwater in the Texas High Plains(Texas Tech University, 2000-12) Kang, Amandeep SinghReese Air Force Base (RAFB), now known as Reese Center is located in the Southern High Plains region of west Texas in Lubbock County. In 1987, concentrations of chlorinated solvents, especially trichloroethene (TCE), were found to be out of compliance with the federal limits. Significant concentrations of perchloroethene (PCE) were also present on site. Pump and treat technologies, which consist of extracting contaminated groundwater and treating it on the surface, have been the traditionally considered technology when significant levels of groundwater contamination exist. Natural attenuation (NA), also called "mtrinsic remediation" has recently been recognized as a potential method for treatment of contaminated groundwater. NA of contaminants includes sorption to soil particles, dilution, dispersion, volatilization, biochemical stabilization, radioactive decay and biodegradation in soils and groundwater. If NA is found to be a viable option at Reese AFB, it can replace the presently employed pump and treat technique and result in monetary gains. A study was conducted to estimate the potential for NA of the TCE present in the Ogallala aquifer at the Reese Air Force Base. Initial assessment of the site showed the existence of three distmct TCE plumes, two on-site and the third off-site. Initial site assessment revealed that one of the plumes exhibited signs of NA. This area is present on-site and consists mostly of the area near the Picnic Lake. A detailed examination of this area was conducted. Plume maps were drawn for the study area using SURFER to study the variation of PCE, TCE, cis-dichloroethene (cis-DCE), and dissolved oxygen (DO) concentrations from 1996 to 1998 (Only data available). These plume maps were then analyzed to study the potential for NA occurring at the site. Data analysis for the study area shows the presence of a large TCE and cis-DCE plume. The TCE plume is located up-gradient and to the northwest of the cis-DCE plume. Data analysis and modeling was used to determme whether the cis-DCE plume is a result of the TCE plume located up-gradient to it. In addition, modeling was used to back track the movement of the TCE plume and locate its possible source as well as assess the future potential of the plume movement.Item Contemporary policy issues in the State of Texas : a series of policy analyses(2015-08) Sandberg, Faith Erin; Rodriguez, Victoria Elizabeth, 1954-; McDaniel Rhodes, DianeThis report is a combination of individual policy analyses on food deserts, groundwater management, teenage pregnancy, and transportation capacity in the State of Texas. Additionally, an analysis on the gender pay gap viewed from the national level is included. These analyses suggest the critical importance of all five issues to the future of Texas as the state faces continued population growth and changing demographics. Furthermore, taken in tandem, these policy issues present an opportunity to reconsider the approach of policymakers working toward achieving social and economic justice. The commonalities amongst these issues suggest that moving from a policy agenda centered around a core of social issues to a broad, all-encompassing agenda that considers the disparate impact of issues like water scarcity and traffic congestion may have a more profound impact on the eradication of social and economic injustice.Item Determination of groundwater velocity in-situ by using passive samplers at sediment water interface(2011-05) Ponnada, Phani; Jackson, Andrew W.; Rainwater, KenContaminated bottom sediments are one of the major sources of contaminants in surface water. The contaminants may originated from human activities, enter the subsurface environment through waste disposal, spills, and land application of chemicals. These contaminants get transported through the porewater and may enter the surface water from the bottom sediments. Establishment of effective remediation systems and protection of public health rely on the ability to estimate the mass flux of the contaminants to surface water. The mass flux is a function of porewater velocity, retardation factor, and degradation coefficient. In this research, passive sampler (peepers) were used to determine the groundwater velocity insitu when the mass flux of the contaminants to surface water was low. This study suggested that the ability of the samplers to accurately capture produced tracer profiles depends on the velocity of the flow and equilibration time of the peeper. Low velocities allowed greater time for the sampler to equilibrate, approaching steady state with the pore water. The sampler was able to serve as a tracer source but was not able to provide a large enough flux of tracer to allow downstream locations to approach the source concentration. Regardless, steady state profiles developed rapidly, likely due to the rapid increase in area available for diffusional flux with distance from the source and the limited flux of source from the sampler cell. A sensitivity analysis indicated that, as expected, diffusional transport dominated at very low velocities and that the source dimensions were the critical determinant of the tracer concentration profile shape. Overall, these studies suggest that it may be possible to differentiate groundwater velocity, but that samplers with very low depths would be required (<0.5cm).Item Economic analysis of the effect of utilizing underground water on the gross income structure of the High Plains area of West Texas and eastern New Mexico, 1929-1959(Texas Tech University, 1961-08) Van Horn, Thomas RNot availableItem Economic impacts of the depletion of the Ogallala Aquifer: an application to the Texas High Plains(Texas Tech University, 1998-08) Terrell, BonnieNot availableItem Environmental effects on quality of leachate from simulated in situ retorted oil shale(Texas Tech University, 1980-08) Barber, Donald RayNot availableItem Evaluation of the aquifer storage and recovery pilot project in Liwa area, Emirate of Abu Dhabi, UAE(2010-12) Khezri, Solaleh; Charbeneau, Randall J.; Herrmann, RolfEmirate of Abu Dhabi is located in an arid region, where the main source of fresh water is desalination plants. The vulnerability of desalination plants renders planning for an alternative source of freshwater essential. In this study the feasibility of aquifer storage and recovery in the Liwa area, in Emirate of Abu Dhabi, United Arab Emirates was investigated. Based on operational data collected from the pilot project, the model was set up and calibrated. The calibrated model was used to study the affect of various operational parameters, namely storage duration, pumping rate, screen location, multiple cycle operation and periodic recharge, as well as some aquifer characteristics factors: dispersion and salinity profile. This study can be utilized to optimize the operation of the Liwa ASR project.Item Experimental evaluation of foam in environmental remediation(2002-05) Rong, Jiann Gwo; Liljestrand, Howard M. (Howard Michael); Rossen, William RichardGround water is the major source of drinking water for many people around the world. Two challenges in subsurface remediation are the removal of nonaqueous phase liquids (NAPL) located in the capillary fringe above the water table and at the bottom of an aquifer. Although several innovative technologies have demonstrated the ability to remove NAPL from source zones, geologic heterogeneities can cause significant NAPL to remain after remediation. The effect of heterogeneity can be mitigated by the application of a mobility-control fluid such as foam. The use of foam as a means of improving remediation efficiency has unique advantages. (1) Foams are inherently stiffer in region of higher permeability. (2) Foams can reduce gravity effects. (3) Foams collapse in the presence of hydrocarbon contaminants. It was found that foam has two different flow regimes in porous media: (a) the high-quality regime and (b) low-quality regime. Steady-state experiments were conducted to study the two foam-flow regimes under low pressure gradient conditions typical of subsurface remediation and identify the effect of various factors on the two regimes. Gas and surfactant solution were co-injected through sandpacks of permeability ranging from 5 to 210 darcy (hydraulic conductivity: 2x10-3 to 5x10-5 cm/sec) in vertical columns. The results confirm that the two foam-flow regimes are present in both the absence and presence of oil in porous media. In the high-quality regime, two factors weakened the foam, decreasing surfactant concentration and the presence of oil. These require an increase of liquid flow rate to maintain a given pressure gradient. In the low-quality regime, as predicted by the fixed-bubble-size model, increasing permeability requires higher gas flow rate to maintain a given pressure gradient. Shear-thinning foam behavior was consistently found in the lowquality regime, while the shear-thinning, Newtonian and shear-thickening foam behavior was observed in the high-quality regime. Lower apparent relative gas permeability was also obtained in higher-permeability porous media.Item Feasibility of variable frequency speed control for irrigation wells(Texas Tech University, 1983-12) Hendrick, Levi KyleNot availableItem Field verification of a dual-porosity flow model to estimate aquifer recharge rates through playa lakes(Texas Tech University, 1996-05) Huda, Akm NazmulThe Southern High Plains of Texas overiies an extensive aquifer known as the Ogallala formation. This aquifer is the prime source of groundwater resources for this region. This aquifer has been experiencing severe depletion of its groundwater reserve due to the intensive use of water for irrigation. The natural recharge of this aquifer primarily depends on the surface mnoff water that is collected by a large number of playa lakes present in this region. The surface mnoff water retained by the playa lakes infiltrates through the playa beds and contributes to the groundwater recharge. However, the actual amount of recharge that takes place through playa beds is difficuh to quantify. Traditionally, recharge through playa lakes was estimated based only on micropore conductivity ofthe soil. However after long dry periods, playa beds tend to develop shrinkage cracks that increases the overall conductivity of soil significantly. Unfortunately, modeling the flow through a macropore system mathematicaUy is very difficult because ofthe complexities in the geometry and the spatial distribution of macropores. In a recent study, a numerical model, FTSCracks, was developed to incorporate the influence of shrinkage cracks on the overall flow rates through unsaturated soils. In FTSCracks, the systems of macropores were defined with some empirical parameters that were difficult to determine through lab tests. In this study, a series of lab and field experiments were performed to verify the FTSCracks model with field and lab data. This study was conducted also to demonstrate the ability of this model in estimation of aquifer recharge.Item Finding a reasonable aquifer yield : support methods for groundwater policy in Texas(2013-05) Petrossian, Rima; Eaton, David J.Managing groundwater can be difficult because there is no common perspective among stakeholders about what they wish for their desired future conditions (DFCs) for Texas' aquifers. Conflicts over how to manage aquifers, whether to mine or sustain groundwater levels are complicated by diverse state and local approaches. This dissertation proposes a decision support method to derive acceptable future aquifer conditions through engaging stakeholders by combining five processes: landowner surveys, stakeholder and decision maker focus groups, contingent valuation, system element identification and scenario-testing. Surveys of water users identified conflicts among water users and decision makers' preferences. For example, how much is groundwater worth in Texas? Responses to two survey questions revealed a willingness to buy groundwater for an average of $2,872 per acre-foot. Most landowners most did not want to sell groundwater at any cost. Those willing to sell revealed an average of $4,069 per acre-foot. A survey of landowners and decision makers indicated that 41 percent of landowners indicated that no new users be issued permits to support stable Trinity Aquifer groundwater levels. Meanwhile, the decision makers chose a DFC of a 30 foot drawdown in the Trinity Aquifer over 50 years. Stakeholder surveys identified the 'best groundwater decision makers' as being the stakeholders or well owners, yet 75 percent of the decision makers preferred the groundwater conservation district board presidents. This suggests that stakeholders would prefer to be the decision makers rather than being asked for their preferences. One decision-maker focus group identified 12 elements representing their understanding of the DFC process. These elements form a system information diagram or preference map. Such a map can help identify alternative pathways for solving problems in the decision process. These complexities remain challenging as Texas moves toward more local regulatory control, more competing interests, and less certainty about Texas' future groundwater supply.Item Freshwater on the island of Maui : system interactions, supply, and demand(2011-05) Grubert, Emily; Webber, Michael E., 1971-; Passalacqua, Paola; King, CareyThis work is part of a broader, multi-year investigation of Maui Island’s freshwater resources. Maui Island faces multiple resource constraints, including water, land, energy, and capital, and these resource constraints could become relevant over the next forty years. Not only does Maui face potential changes to its water and other systems due to external factors beyond its control, like anthropogenic and other climate changes, but Maui also could make developmental choices that will impact how its resource systems interact. In particular, this work looks at Maui’s freshwater systems as they relate to energy, waste, and environmental systems. This report provides a foundation for future scenario analysis on the island that will aim to characterize potential synergies and hazards of choices like increased food production, local fuel production, and increased use of renewable energies.Item Geochemical evolution of uraniferous soda lakes in Eastern Mongolia(2008-12) Linhoff, Benjamin Shawn; Bennett, Philip C. (Philip Charles), 1959-Extremely high concentrations of U were discovered in hypersaline soda lakes in eastern Mongolia. The lakes are small, shallow (<1km², <1m), and terminal with variable salinity. The origin and fate of U in these lakes was investigated using geochemical analyses and modeling, using samples collected from lakes and lake pore waters, wells and a stream. Samples were analyzed for Sr and U isotopes, cations, trace metals, anions, total inorganic carbon (TIC), and unstable field parameters. A representative groundwater in the field area is dilute and alkaline, with pH=7.9, 10 mmol L⁻¹ of TIC and 5 mmol L⁻¹ Cl⁻. In contrast, a representative lake water is pH(similar to)10 with TIC and Cl⁻ each more than 1000 mmol L⁻¹. Uranium concentrations in lake waters range from 0.24 to more than 62.5 (Greek small letter mu)mol L⁻¹, possibly making these lakes the highest naturally occurring U concentrations ever reported in a natural water. Groundwater concentrations of U range from 0.03 and 0.43 (Greek small letter mu)mol L⁻¹. The U is natural and derived from groundwater discharging to stable closed basin lakes. Waters are concentrated by evaporation and U(VI) is chelated by CO₃⁻² to form the highly soluble UO₂(CO₃)₃⁻⁴. Two sets of well waters with corresponding lake discharge waters were analyzed for U isotopes. Unnatural concentrations of ²³⁵U were tested for, the presence of which would indicate fallout-derived U. The average of four samples was ²³⁸U/²³⁵U=136(plus or minus)2 indicating that the U is naturally derived. (Greek small letter delta)²³⁴U between one well and its corresponding discharge lake had similar (Greek small letter delta)²³⁴U values ([Greek small letter delta]²³⁴U=837.6- 858.5). The other sample pair however, revealed significant differences between the well and its discharge lake ([Greek small letter delta] ²³⁴U=303.6-1530). This suggests nuclide recoil is significantly enriching one of the lakes with ²³⁴U beyond secular equilibrium during alpha-decay of ²³⁸U in lake sediments or along the groundwater flow path. Modeled evaporation of lakes demonstrates that a U-mineral phase is likely to precipitate during evaporation. Strontium isotopes varied in groundwaters between ⁸⁷Sr/⁸⁶Sr= 0.706192-0.709776 and in lakes ⁸⁷Sr/⁸⁶Sr=0.708702-0.709432. Cretaceous mafic rocks likely account for low ⁸⁷Sr/⁸⁶Sr values while Cretaceous alkaline rhyolites account for the high ⁸⁷Sr/⁸⁶Sr values. High concentrations of U, Na, Cl⁻, and K correlate to radiogenic Sr in lake waters indicating that U is sourced from local Cretaceous alkaline rhyolites.Item Ground Water Leaching of In Situ Retorted Oil Shale(Texas Tech University, 1977-12) Watts, Jackie CarrolNot Available.Item Groundwater dynamics and surface water-groundwater interaction in a prograding delta island, Louisiana, USA(2014-05) O'Connor, Michael Thomas; Moffett, Kevan B.Delta islands make up the majority of coastal delta area. However, the groundwater hydrology of young, prograding delta systems and its relationship to surrounding surface water dynamics are poorly understood. Deltas in coastal environments are assumed to function as chemical “buffers”, filtering nutrient-rich terrestrial runoff through the island structures and surface water ecosystems as it travels to the sea, but the magnitude of this effect cannot be accurately quantified without understanding the physical relationships between the surface water and groundwater. This study developed the first conceptual model of the hydrology of prograding delta island groundwater systems. The study was based on field data collected at Pintail Island, a 2 km2 island within the Wax Lake Delta in Louisiana. Hydraulic properties and processes were quantified at multiple depths at locations spanning the island elevation gradient. Groundwater and surface water levels were monitored. A weather station recorded precipitation, air, and wind conditions. The groundwater within Pintail Island was both spatially and temporally dynamic throughout the study period of Sept/9/2013 to Feb/4/2014. The aquifer within the distal limbs of the island responded as a connected, saturated unconfined aquifer. The portions of Pintail Island within the older, proximal, higher elevation apex were found to be a two-layer system with fine sediments and organic matter overlying sandy deposits. The aquifer within this section of the island responded differently during times of elevated surface water (storm events) and times of normal surface water (calm periods) and differently from the distal-island unconfined system. The fine, shallow (roughly 0-60cm depth) sediments capping this older, higher portion of the island appeared to inhibit vertical flow between the surface and subsurface, creating semi-confined conditions within the sands in the deeper island subsurface. High water levels led to overpressurization of the apical aquifer, which was maintained between storms due to the low hydraulic gradient and the low permeability of the porous medium. During inundating storm events, groundwater potentials mimicked surrounding surface water levels. This conceptual model of a prograding coastal delta island now provides a foundation for further, hydrologically-realistic study of delta ecology and nutrient exchange.Item Groundwater flow controls on coastal water quality and global groundwater ages(2015-05) Befus, Kevin Martin; Cardenas, Meinhard Bayani, 1977-; Gleeson, Thomas P; Hesse, Marc A; Paine, Jeffrey G; Sharp, John MHumanity relies on groundwater. But, current consumption may be outpacing groundwater renewal rates, and anthropogenic activities are altering its quality. This dissertation advances the state of knowledge of how local and regional groundwater dynamics affect its quality and quantity. First, I investigate groundwater discharge patterns and fluxes in three lakes in the Nebraska Sand Hills region and on the island of Rarotonga, Cook Islands, to understand the hydrologic connection between groundwater and surface water in these lacustrine and coastal settings. In Nebraska, I use electrical geophysical methods to characterize the spatial signature of groundwater recharge and discharge to and from the lakes using groundwater salinity patterns. On Rarotonga, a detailed field study of groundwater flow at the intertidal zone shows how groundwater flow influences the thermal regimes of nearshore environments, affecting the biota that live and chemical processes that occur near and below this dynamic interface. Next, a dense network of geophysical surveys across the coastal plain and into the lagoon on Rarotonga constrains multiple features of the larger-scale hydrologic system that are primarily controlled by the local carbonate and volcanic geology on the island. Finally, I give the first estimate of the global storage and spatial distribution of groundwater with a mean age since recharge of less than fifty years. I use several thousand two-dimensional groundwater flow and age-as-mass transport simulations parameterized by the best available hydrologic and geologic datasets. This global analysis suggested that ~6% of the groundwater stored in the upper 2 km of the Earth’s crust is younger than 50 years. Comparing this young groundwater storage to current groundwater depletion rates indicates that more than half of the irrigated areas depending significantly on groundwater could have already used up all of the young groundwater and are using groundwater more quickly than the storage is replenished. Together, these studies advance how to quantify groundwater as a renewable resource through the global estimation of groundwater storage associated with certain timespans and by analyzing the implications of groundwater flow on water quantity and quality in field settings.Item Groundwater inflow into rock tunnels(2010-08) Chen, Ran; Tonon, Fulvio; Rathje, Ellen; Eichhubl, Peter; Sharp, John M.; Zornberg, Jorge G.Prediction of groundwater inflow into rock tunnels is one of the essential tasks of tunnel engineering. Currently, most of the methods used in the industry are typically based on continuum models, whether analytical, semi-empirical, or numerical. As a consequence, a regular flow along the tunnel is commonly predicted. There are also some discrete fracture network methods based on a discontinous model, which typically yield regular flow or random flow along the tunnel. However, it was observed that, in hard rock tunnels, flow usually concentrates in some areas, and much of the tunnel is dry. The reason is that, in hard rock, most of the water flows in rock fractures and fractures typically occur in a clustered pattern rather than in a regular or random pattern. A new method is developed in this work, which can model the fracture clustering and reproduce the flow concentration. After elaborate literature review, a new algorithm is developed to simulate fractures with clustering properties by using geostatistics. Then, a discrete fracture network is built and simplified. In order to solve the flow problem in the discrete fracture network, an existing analytical-numercial method is improved. Two case studies illustrate the procedure of fracture simulation. Several ideal tunnel cases and one real tunnel project are used to validate the flow analysis. It is found that fracture clustering can be modeled and flow concentration can be reproduced by using the proposed technique.
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